biology

Soil-transmitted helminth

Soil-transmitted helminth is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Soil-transmitted helminth rather than just read about it. In short: The soil-transmitted helminths (also called geohelminths) are a group of intestinal parasites belonging to the phylum Nematoda that are transmitted primarily through contaminated soil. They are so called because they have a direct life cycle which requires no intermediate hosts or vectors, and the parasitic infection occurs through faecal contamination of soil, foodstuffs and water supplies.

Key takeaways

Soil-transmitted helminth belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Soil-transmitted helminth to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Soil-transmitted helminth from memory before moving on to harder problems.

Reference excerpt

The soil-transmitted helminths (also called geohelminths) are a group of intestinal parasites belonging to the phylum Nematoda that are transmitted primarily through contaminated soil. They are so called because they have a direct life cycle which requires no intermediate hosts or vectors, and the parasitic infection occurs through faecal contamination of soil, foodstuffs and water supplies. The adult forms are essentially parasites of humans, causing soil-transmitted helminthiasis (STH), but also infect domesticated mammals. The juveniles are the infective forms and they undergo tissue-migratory stages during which they invade vital organs such as lungs and liver. Thus the disease manifestations can be both local and systemic. The geohelminths together present an enormous infection burden on humanity, amounting to 135,000 deaths every year, and persistent infection of more than two billion people.

Species Soil-transmitted helminths are typically from the following families of nematodes, namely:

Roundworms (family Ascarididae), e.g. Ascaris lumbricoides Whipworms (family Trichuridae), e.g. Trichuris trichiura Hookworms (family Ancylostomatidae), e.g. Ancylostoma duodenale and Necator americanus Threadworms (family Strongyloididae), e.g. Strongyloides stercoralis

Diseases

Soil-transmitted helminthiasis

Soil-transmitted helminthiasis is a collective name for the diseases caused by ascaris, whipworm and hookworms in humans. It includes species-specific diseases such as

Ascariasis, which is caused by Ascaris lumbricoides Hookworm diseases (ancylostomiasis and necatoriasis), which are caused by Necator americanus and Ancylostoma duodenale Trichuriasis, which is caused by Trichuris trichiura Soil-transmitted helminthiasis is classified as one of the neglected tropical diseases projected to be controlled/eradicated by 2020 through the London Declaration on Neglected Tropical Diseases.

Strongyloidiasis

This is caused by Strongyloides stercoralis. Even though the disease is principally a soil-transmitted helminthiasis, the infection being mediated through contaminated soil, it is however generally omitted in clinical practices and control programmes because of its (allegedly) relatively less significant influence on health and socio-economic conditions. Also it is not restricted to humans, as it is common in pets. But there is an emerging hyperinfection syndrome caused by S. stercoralis, which exhibits a high mortality rate (15% to 87%).

General impact Geohelminth infection is a major health problem particularly in rural areas of developing countries like Subsaharan Africa, India and other Southeast Asian countries. It is an important cause of morbidity in school age children who harbour the highest intensity of worm infestation. Some of the significant morbidity attributed to intestinal helminthiasis are malnutrition, growth retardation, anaemia, vitamin A deficiency and impaired intellectual performance.

Control activities The World Health Organization is promoting the control of soil transmitted helminthiasis with large scale, regular distribution of anthelminthics (albendazole or mebendazole) to the population groups more at risk of morbidity (children and women of reproductive age). The number of school-age children treated with PC has progressed steadily from less than 120 million in 2008 to over 450 million in 2018 and is in continuous expansion.

References

External links WHO information page USAID's Soil-Transmitted Helminth Program World Health Organisation (WHO) topic page on helminthiasis

Worked examples

Example 1 — a first encounter with Soil-transmitted helminth

Start with the simplest possible case. Write down what Soil-transmitted helminth claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Soil-transmitted helminth before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Soil-transmitted helminth ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Soil-transmitted helminth

In research: Soil-transmitted helminth appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Soil-transmitted helminth in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Soil-transmitted helminth is common in secondary-school and first-year university syllabi. It links to neighbouring topics Conditions diagnosed by stool test, Foodborne illnesses, Helminthiases, so understanding it makes those chapters shorter.
In everyday life: Look for Soil-transmitted helminth outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Soil-transmitted helminth in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Soil-transmitted helminth means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Soil-transmitted helminth out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Soil-transmitted helminth in simple terms?

Why does Soil-transmitted helminth matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Soil-transmitted helminth?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Soil-transmitted helminth.